Mobile elements Torin 1 supplier play an important role in the diversification of bacterial genomes. One important group of mobile genetic elements is the Tn916 family of conjugative transposons (also known as integrative and conjugative elements [ICEs]) [18]. These conjugative transposons usually code for tetracycline resistance and are found primarily in the Firmicutes. Numerous transposons have been described to be present in C. difficile genomes [5, 7, 11, 17, 19]. Several elements closely related to Tn916 are present in diverse C. difficile strains, including Tn5397 which confers tetracycline resistance [20, 21]. Other transposons have been described to confer resistance to chloramphenicol

and erythromycin [5]. Recently, the first full length genome of a PCR ribotype 078 strain was published [5]. This M120 strain has been isolated from an Irish diarrheic patient. It was shown that PCR ribotype 078 is highly divergent from PCR ribotype 027, 001, 017 and 012. In addition, this PCR ribotype 078 strain was described to contain a unique 100 kb insert that showed 80% similarity to sequences of Thermoanaerobacter species and Streptococcus pneumoniae[5]. In this paper we show that the 100 kb insert is a mobile element that

is only sporadically present in PCR ribotype 078 strains. Furthermore, we show that the 100 kb consists of at least two independent mobile elements that were fused during evolution. Results Previously, an insert, unique for C. difficile, was described in the genome of strain M120, a PCR ribotype 078 strain, GPCR Compound Library chemical structure isolated Fossariinae from an Irish diarrheic patient [5]. We analyzed the open reading frames (ORFs) present in the insert to investigate their nature and origin (see Figure 1 and Table 1). Figure 1 Schematic view of full Tn 6164 (top panel) and half the element (bottom panel) and its open reading frames, flanked by C. difficile regions. Various parts of the insert are colored

according to their homology. White, C. difficile; Red, Module A; Yellow, Module B; Purple, Module C; Orange, Module D; Blue, Module E; black, unknown. Location of the oligonucleotides used for the data in Table 2 is indicated by arrowheads Table 1 Open reading frames encoded by Tn 6164 Gene Position on Tn 6164 Module Sequence identity to Annotation Gene Position on Tn 6164 Module Sequence identity to Annotation Orf1 650-1930 A – putative modification methylase Orf25 26793-27122 B – conserved hypothetical protein Orf2 1915-3186 A – putative modification methylase Orf26 27189-28451 B Thermoanaerobacter sp. HK97 family phage portal protein Orf3 3252-3962 A – hypothetical protein Orf27 28448-29128 B Thermoanaerobacter sp. Peptidase S14, ClpP Orf4 3952-5031 A – ATPase associated with various cellular activities Orf28 29140-30339 B Thermoanaerobacter sp.